The present invention generally relates to electrical connections between electrical circuit components and, more particularly, relates to a flat electrical terminal for connecting first and second circuit elements.
It is generally common, particularly in the automotive industry, to employ flat leaded terminals (pins) for connecting electrical circuitry in dual in-line packages (DIP), single in-line packages (SIP), and flat pin array (FPA) packages. These types of electrical circuitry packages often employ electrically conductive flat wire terminals, also referred to as leads or pins, that typically are either clipped to the side of a substrate, surface mounted to the substrate, or soldered through plated vias. Flat terminals are generally inexpensive and are widely used in the electronics industry due to the relative ease of use in many applications.
The flat terminals generally have a difference in accumulative cross-sectional modulus of the terminals in the X and Y-axes, when the terminal is oriented in the Z-axis, due to the orientation of the flat terminals with respect to the substrate. This is particularly evident with wider and heavier terminals capable of handling high currents. As a consequence, the DIP, SIP, and FPA package and electrical connections at the terminals exhibit high bending resistance in the axis aligned with the flat side of the terminal, and much lower bending resistance in the axis normal to the flat side of the terminal. This difference in modulus can produce different amplitudes of motion in each axis when vibrations occur which can further result in accumulative fatigue in the terminals and connecting solder joints due to the greater terminal bending along the weaker modulus direction.
Additionally, differences in the coefficient of thermal expansion (CTE) of circuit boards can create differences in axial aligned modulus which can produce greater tendency to break terminal-to-pad solder joints due to stress risers aligned in the plane of higher cross-sectional modulus. When subjected to stress and vibration, the electrical circuitry packages are generally susceptible to electrical contact weakening and possible failure. As a consequence, conventional electrical circuitry packages typically require secondary support structures. Other approaches to interconnecting electrical circuits in such packages may include the use of round or square cross-sectional pins (terminals). However, round and square cross-sectional pins are generally more expensive, require additional conductive material, and, such pins must be attached to press on solder clips that allow the terminals to be attached to the substrate, which adds to the manufacturing costs.
It is therefore desirable to provide for an enhanced low cost electrical connection between first and second circuit elements using flat terminals which offers improved response to vibration stimulus, reduced solder pad stresses, and minimize the need for secondary support structures.
In accordance with the teachings of the present invention, an electrical terminal is provided for connecting a first circuit element to a second circuit element. The terminal includes a flat conductive member having a first end for connecting to a first circuit element and a second end for connecting to a second circuit element. The conductive member has a twisted section between the first and second ends that is axially twisted through an angle in the range of forty-five to one hundred thirty-five degrees (45xc2x0-135xc2x0).
According to another aspect of the present invention, a method of providing an electrical interconnection between first and second circuit element with a twisted flat terminal is provided. The method includes the steps of providing a first circuit element, providing a second circuit elements, and axially twisting a flat conductive terminal through an angle in the range of about forty-five to one hundred thirty-five degrees (45xc2x0-135xc2x0) about its longitudinal axis. The method further includes the steps of connecting a first end of the conductive terminal to the first circuit element, and connecting a second end of the conductive terminal to the second circuit element.
The electrical terminal and method of the present invention offers a low cost electrical connection that improves overall stress/fatigue performance. By twisting the flat terminal, the electrical interconnection improves response to vibration stimulus, reduces the solder pad stresses for electrical connections, and minimizes the need for secondary support structures.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.